Polycarbonates are polymers in which aromatic or aliphatic dioxy compounds are connected to each other by a carbonate ester, and a polycarbonate obtained from 2,2-bis(4-hydroxyphenyl)propane (commonly known as bisphenol A) out of these is used in many fields as it is excellent in not only transparency and heat resistance but also mechanical properties such as impact resistance.
Polycarbonates are generally produced from raw materials obtained from oil resources. Since the depletion of oil resources is now concerned, a polycarbonate obtained by using an ether diol produced from sugar which is a biogenic matter is now under study.
For example, Patent Document 1 proposes a homopolycarbonate having a melting point of 203° C., which is produced by using a melt transesterification process. Patent Document 2 proposes a polycarbonate having a glass transition temperature of 170° C. or higher, which is produced by using a tin catalyst. Patent Document 3 proposes a copolycarbonate of isosorbide and a linear aliphatic diol.
When the development of the industrial application of these polycarbonates comprising isosorbide is taken into consideration, impact resistance must be improved. For example, the ISO179 notched Charpy impact strength of isosorbide homopolycarbonate having a specific viscosity of 0.33 is about 6 kJ/m2. This value is unsatisfactory for industrial application and must be improved.
In general, impact resistance greatly depends on the molecular weight (=specific viscosity) of a resin. Therefore, to improve impact resistance, the molecular weight of the resin must be increased. The isosorbide polycarbonate described in the above Patent Documents 1 and 2 has a problem that molding becomes difficult as the melt viscosity of the resin becomes too high when the molecular weight is increased. As for the polycarbonate of Patent Document 3, the ISO179 notched Charpy impact strength of the polycarbonate having a reduced viscosity of about 0.9 of Example 6 is about 7 kJ/m2. This value is unsatisfactory for industrial application and must be improved.
Patent Document 4 proposes a resin composition prepared by adding an addition polymerization polymer such as ABS resin to isosorbide polycarbonate. However, when ABS resin is added, impact resistance is improved but the heat resistance and transparency of the polycarbonate greatly deteriorate.
Patent Document 5 proposes a resin composition which has improved impact resistance, low melt viscosity and excellent heat resistance, heat stability and moldability, which is obtained by adding a rubbery polymer to a polycarbonate derived from an ether diol such as isosorbide. However, Patent Document 5 is silent about transparency.
Patent Document 6 discloses a method of providing impact resistance without impairing the transparency of the isosorbide polycarbonate by adding core-shell rubber to isosorbide polycarbonate. However, since the haze of the obtained molded article is high, it cannot be said that transparency is satisfactory for molded articles for optical use which require extremely high transparency. Further, the above Patent Document 6 discloses a resin composition having transparency, impact resistance and heat resistance, which is prepared by finely dispersing a soft styrene-based resin having an average refractive index difference of ±0.015 or less into isosorbide polycarbonate. However, a molded article of the obtained resin composition is a 0.1 mm-thick film, and a method of improving the impact resistance of a large-sized molded product obtained by injection molding or extrusion molding while retaining its transparency is not disclosed.
(Patent Document 1) British Patent Application No. 1079686
(Patent Document 2) WO2007/013463
(Patent Document 3) WO2004/111106
(Patent Document 4) JP-A 2007-070438
(Patent Document 5) WO2008/146719
(Patent Document 6) WO2012/008344